A note on the predominance of dynamic strain-ageing over the adiabatic shear deformation phenomenon in commercial purity titanium in compression tests at strain rates of 0.05 to 32 s −1 and temperatures of 303 to 573 K

Abstract

Recently, Venugopal et al. ( J. Mater. Process. Technol., 21 (1990) 201) reported that commercial purity titanium exhibits loss in ductility during compression testing at particular combinations of temperature (in the range 373 to 573 K) and strain rate (in the range 0.05 to 32 s −1), the authors explaining the loss in ductility in terms of dynamic strain-ageing. The microstructures of many of the deformed samples reported by them showed shear bands, such microstructures and the reported characteristics of adiabatic shear deformation indicating that the adiabatic shear deformation that occurs readily in titanium in the temperature and strain-rate regime investigation may be responsible also for the loss in ductility of the material. In this communication the characteristics of the adiabatic shear deformation phenomenon reported in the literature are compared with the characteristics reported by Venugopal et al., the comparison revealing that dynamic strain-ageing is more predominant than adiabatic shear deformation in the behaviour of the material during compression testing in the above mentioned temperature and strain-rate regime. Room temperature tensile tests at strain rates of 0.05 and 0.11 s −1 were conducted on the same material to study the strength differential effect (SD effect), a pronounced level of such effect being observed, this result serving to confirm that dynamic strain-ageing is more predominant than adiabatic shear deformation in commercial purity titanium during compression testing in the temperature and strain-rate regime investigated.